The invention relates to a filter, particularly a liquid filter, e.g., for filtering fuels, such as gasoline or diesel, for internal combustion engines.
Modern internal combustion engines make ever-increasing demands on the fluids used, such as oil, or the fuels gasoline and diesel. Modern injection systems of Otto and diesel engines are sensitive to even the smallest impurities in the fuel. Damage to the injection systems can occur as a result of particle erosion and corrosion due to water contained in the fuel. One function of the fuel filters, in addition to particle filtration, can also be the removal of water from the fuel.
Corrosion due to water content is particularly problematic in diesel engines. Water content in diesel fuel can range from 200 ppm to 2 percent. Water can be present in the fuel in free or stably emulsified form. In modern diesel engines, fuel is normally injected directly into the cylinders. A distinction is drawn primarily between pump nozzle systems, common rail systems and direct injection with solenoid valve-controlled distributor injection pumps, the latter being increasingly rare. Common rail systems and distributor injection pumps are particularly sensitive to high water contents in the fuel because the fuel remains longer in the injection system. Pump nozzle systems require water separation only if a large amount of water is expected.
Water droplets normally separate in the fuel filter along the fibers of the filter medium and aggregate to increasingly larger droplets. The droplets flow down along the outside and partly along the inside of the filter pleats because of their higher density compared to that of the fuel. The water collects in a liquid collection space, a water collection space, that is normally disposed below the filter medium. From this water collection space, the water can then be removed, for example using a valve, without the entire filter having to be changed.
There are various embodiments of the filter and the configuration of a liquid collection space below a filter element within a filter.
U.S. Pat. No. 5,904,844 describes a fuel filter with a two-part housing. The first part of the housing holds the filter medium. The filter medium is at least partly supported in the lower region of the first part of the housing. A second part forming the water collection space is screwed onto to the lower end of the first part of the housing. A disadvantage of the construction of the filter of the '844 patent is that the filter body cannot be manufactured in one piece. Threads or connecting devices and seals are required between the first part of the housing with the filter medium and the second part of the housing with the water collection space.
German patent application no. DE 100 29 539, for example, discloses a filter with an annular filter medium. The filter medium is disposed in the upper region of the housing and a spacer for the filter element is provided in the lower region. The spacer has a spring element. The spacer ensures that a collection space can be formed for the separated water. The housing in which the filter medium and the spacer are located can be formed of a single piece and closed by a lid.